Selective Transport of Plasma-Derived Reactive Species through the Plant Aquaporin Channels: A Molecular Dynamics Study

The selective permeability of reactive oxygen and nitrogen species (RONS), generated by cold atmospheric plasma (CAP), through plant aquaporins was investigated to identify plasma-derived species capable of intracellular delivery. Using atomistic molecular dynamics and enhanced sampling methods, we quantified the free energy profiles of eight RONS (HNO3, HO2, cis-HNO2, trans-HNO2, N2O4, NO, NO2, and O3) across the PIP2;1 aquaporin channel embedded in a lipid bilayer. Hydrophobic species such as NO and O3 exhibited minimal energy barriers (~1-2 kJ{middle dot}mol-1) facilitating rapid permeation, while polar and bulky molecules like HNO3 and N2O4 encounter substantial energy barriers (>15 kJ{middle dot}mol-1), particularly near the selective region (also known as the ar/R constriction), which acts like a filter to control what can pass through the aquaporin. These results reveal that RONS permeability is governed by molecular size, polarity, and hydrogen bonding capacity. This mechanistic insight enables rational selection of CAP-generated species for enhancing plant uptake efficiency, with implications for sustainable plasma-based agricultural technologies.